Childbearing beyond age 40: pregnancy outcome in 24,032 cases.

OBJECTIVE: To examine pregnancy outcomes in women age 40 or older.
METHODS: We used data from the California Health Information for Policy Project, which consists of linked records from the birth certificate and the hospital discharge record of both mother and newborn of all births that occurred in acute care civilian hospitals in California between January 1, 1992, and December 31, 1993. The study population consisted of all women who delivered at age 40 or over. The control population was women who delivered between age 20 and 29 years during this 2-year period. We reviewed gestational age at delivery, birth weight, mode and type of delivery, discharge summary and birth certificate demographics, birth outcome, pregnancy, and delivery data.
RESULTS: Approximately 1,160,000 women delivered during the study period, and 24,032 (2%) of these women were age 40 or older. Of this latter group, 4777 (20%) were nulliparous. The cesarean delivery rate for nulliparous women in the study population was 47.0%, and the rate for multiparous patients in this group was 29.6%. The cesarean delivery rate was 22.5% for nulliparous and 17.8% for multiparous women in the control group. In the older group, the operative vaginal delivery rate (forceps and vacuum) was 14.2% for nulliparous women and 6.3% for multiparous women. Rates of birth asphyxia, fetal growth restriction, malpresentation, and gestational diabetes were significantly higher among older nulliparas (6, 2.5, 11, and 7%, respectively) compared with rates among control nulliparas (4, 1.4, 6, and 1.7%, respectively), and there were similar significant increases among older multiparas (3.4, 1.4, 6.9, and 7.8%, respectively), compared with younger multiparous controls (2.4, 1, 3.7, and 1.6%, respectively). Mean (+/- standard error) birth weight of infants delivered by older nulliparous women was 3201+/-10 g, significantly lower than that among nulliparous controls (3317+/-1 g), whereas mean birth weight in the group of older multiparas (3381+/-5 g) was no different than that among younger multiparous controls (3387+/-1 g). Gestational age at delivery was significantly lower among older nulliparas (273.4+/-0.4 days), compared with nulliparous controls (278.5+/-0.05 days), and similarly lower among older multiparous women (274.0+/-0.2 days), compared with multiparous controls (278.3+/-0.05 days). More white women age 40 or over than younger white women were having a first child (64 and 39%, respectively).
CONCLUSION: Nulliparous women age 40 or over have a higher risk of operative delivery (cesarean, forceps, and vacuum deliveries: 61%) than do younger nulliparous women (35%). This increase occurs in spite of lower birth weight and gestational age and may be explained largely by the increase in other complications of pregnancy. The increased frequency at which white women are having their first child at age 40 or over may reflect career choices that involve delaying childbirth until the fifth decade of life. These data will allow us better to counsel patients about their pregnancy expectations and possible outcomes.